Fool’s gold? Why blinded trials are not always best

The essence of blinding is withholding information about treatment assignment from people involved in the trial. Trials in which patients, clinicians, and researchers are blinded to the allocated intervention are usually regarded as the gold standard of clinical research and evidence.12 However, blinding’s illustrious reputation brings with it the danger that it is regarded as essential for a trial to be “good,” especially if users place an uncritical reliance on hierarchies of evidence in which blinded evaluations are near the top.3 Given that the number of new trials is increasing every year, with 25 000 registered since the start of 2019, we are concerned that a substantial amount of time, energy, and funding may be going into considering and implementing blinding without a sound rationale for it.4

Past, present, and future trials contain vast amounts of important data. If trials without blinding are inappropriately judged to be of lower quality than blinded trials then we may not be making best use of their data to improve healthcare, while blinded trials may be producing results that are more difficult to interpret than they need be. In this article, we seek to stimulate debate by challenging some of the prevailing beliefs on the benefits of blinding.